1. Field of the Invention
The present invention relates to an image forming apparatus which is applied as an electrophotographic copying machine, and an image forming method.
2. Description of the Related Art
In this kind of image forming apparatus, an electrostatic latent image is formed on a photoconductor drum as an image holding element, and the latent image is developed as a toner image by a developing unit. The toner image is transferred to a paper sheet in a transfer unit. The toner remained on the photoconductor drum at the time of transfer is eliminated by a cleaning unit.
In a certain image forming apparatus, a toner replenish device replenishes a developing unit with fresh toner, and a toner collection mechanism collects the toner eliminated by a cleaning unit and supplies the collected toner to a developing unit for reusing.
A developing unit contains a developing roller in a developer reservoir, and has first and second mixers as first and second stirring and carrying members.
The first mixer rotates to stir and carry a developer in a first direction from one end side to the other end side, and supplies the developer to a developing roller. The second mixer rotates to carry the developer in a second direction reverse to the first direction, and circulates the developer to the first mixer.
Fresh toner replenished by the toner replenish device and recycled toner collected by the toner collection mechanism are fed to one end side of the second mixer, and stirred and carried as described in U.S. Pat. No. 6,577,824.
However, in the prior art, as replenished toner and recycled toner are fed to one end side of the second mixer, in which they are mixed, stirred and carried, the replenished fresh toner is sufficiently charged, but the recycled toner is not sufficiently changed.
The replenished toner is fresh, and can be sufficiently charged at the stirring and carrying speed given by the rotation of the second mixer. But, the recycled toner is often degraded, and cannot be sufficiently charged at the stirring and carrying speed of the second motor. Thus, good development is not expected.